Analysis of parallel groove clamp with finite element method

Due to its simple structure, easy installation and low cost, bolt-type power connector, the parallel groove clamp is widely used in overhead power transmission and distribution lines. However, due to high and fluctuating current loads and harsh environments in China, there are many problems in application of this kind of connector. After analysis of failed connectors collected from Chinese overhead power lines, the main failure causes were found (Luo et al., 1999). For further understanding and simulation in the lab, electrical current tests for parallel groove clamps were conducted and finite element analysis was used to simulate the failure process. Some useful results are summarized and described in this paper. (1) Bolt tension force linearly increases with temperature rise. The force increase rate is up to 43.98 N//spl deg/C. Thus, oxidation on contact surfaces is accelerated and contact resistance increases accordingly. (2) Vibration model FEM analysis shows that there are many kinds of vibration modes for parallel groove clamps, including clamp shaking, rocking and swinging and relative motion between upper and lower covers. The scope of mode frequency is close to vibration of overhead power lines induced by wind, which may cause two-thirds of failed samples with obvious fretting wear morphology at contact interfaces. (3) Imbalance of contact resistance among clamps and connected wires may cause electric current to pass through the bolts, increasing temperature rise and accelerating bolt stress relaxation. (4) Contact force, film resistance and fretting at the contact interfaces are the key points of connector failure.